Wetting device for offset printing machines



Aug. 22, 1961 R. REINARTZ ETAL 2,996,981

WETTING DEVICE FOR OFFSET PRINTING MACHINES Filed Feb. 15, 1960INVENTORS HRMANK FI'sc her;

United States Patent 2,996,981 WETTING DEVICE FOR OFFSET PRINTINGMACHINES Robert Reinartz and Hermann Fischer, Augsburg, Germany,assignors to Maschinenfabrik Augsburg-Numberg, A.G., Augsburg, GermanyFiled Feb. 15, 1960, Ser. No. 8,809 Claims priority, application GermanyMar. 5, 1959 7 Claims. (Cl. 101-148) This invention relates to a wettingdevice for offset printing machines. In particular, the invention isdirected to a ductor roller which is immersed in a water tank, withmoisture being taken from the ductor roller by intermittent contact witha swinging roller and passed to the distributing and inking rollers. Themoisture applying surface of the ductor roller is composed of a numberof independently movable and/or spaced rings.

In offset printing, the need for moisture varies factual- 1y with thedifference in size of the inking surfaces. The control of the moistureis, on one hand, achieved by a smooth or stepless shifting forward ofthe ductor roller in a peripheral direction and, on the other hand, by avariation in the quantity of moisture along the longitudinal length ofthe ductor roller. In the latter case, squeezing rollers of differentwidths and in different numbers have been used to squeeze off the waterat the places in whose area there are larger inking surfaces on theoffset plate which require less water. This is an expensive andtime-consuming method and does not permit an accurate regulation of themoisture so that excess water enters the inking apparatus, combines withthe ink to form an emulsion, and thus results in a poor print. Also,narrow felt rings or leaf springs have been applied against the ductorroller or air blast nozzles located closely side by side were mountedalong the ductor roller, with the individual nozzles being opened wherenecessary to blow off excess wetting water. Again, ductor rollers havebeen used which are composed of series of brushes which are dividedalong the longitudinal length of the roller into individual brushsections which can be arranged as desired. Furthermore, wetting devicesexist in which nozzles are used to spray a wet mist, with the individualnozzles being opened and closed in the desired positions. Anotherconventional wetting device is a distributing roller having its liquidapplying surface divided into ring-shaped zones extendingperpendicularly to the longitudinal axis of the roller. All of theseknown devices do not give a practically satisfactory application of themoisture.

The object of this invention is to produce a ductor roller which willaccurately apply the quantity of moisture desired on certain areas ofthe printing plate.

According to this invention, the disadvantages of the prior art areovercome by using a ductor roller immersed in a water tank with theroller having a moisture applying surface composed of a number ofindependent movable or exchangeable spaced rings whose circumferentialsurfaces lie in planes which are inclined with respect to thelongitudinal axis of the shaft of the ductor roller. The adjacent ringsare spaced from each other a distance, at most, such that a continuousfilm of liquid is drawn off the swinging transfer roller during onerevolution of the ductor roller. By this means, a locally concentratedor small quantity of water can be applied by means of a simple lateraldisplacement of the rings on the ductor roller, with the small width ofthe rings permitting a precise gradation of the water transferred fromthe roller. The inclination of the ring surfaces achieves simultaneouslya laterally displaced application of the strip of moisture so that theannular concentration of the liquid produced by ring surfacesperpendicular to the axis of the roller is avoided. The invention alsomakes it possible to obtain a more uniform distribution of the moistureover the whole length of the roller by spacing the inclined rings moreclosely toward the ends of the roller. As the area of the moistureapplying surface of the roller can be varied, squeezing becomesunnecessary so that the considerable wear and tear on the ductorcylinder linings is reduced. This invention also has the advantage inthat the position of the rings can be correctly adjusted as determinedby the variation in the quantity of wetting liquid required inproportion to the size of the applying surface, whereas in air blastregulation, the moisture quantity depends, not only upon the number ofthe nozzles, but also upon the intensity of the air blast and the speedof the printing press.

A washing device for cleaning ductor rollers is known which has inclinedgroves in a roller in order to produce a squeezing effect on the ductorroller. However, these grooves are out so as to be chevron-shaped orarrowpointed. Grooves of this kind do not permit a proportioneddistribution of moisture taken from the ductor roller.

The means by which the objects of the invention are obtained aredisclosed more fully with reference to the accompanying drawings, inwhich:

FIGURE 1 is a front view of the ductor roller partly shown in section;

FIGURE 2. is a cross-sectional view on the line 22 of FIGURE 1; and

FIGURE 3 is a front view of a wetting ring partially broken away.

Ductor roller 1 is mounted in the press frames 2 and 3 and partiallyimmersed in a water tank 4. Water picked up by the ductor roller istransferred by a swinging roll 5 in a conventional manner to thedistributing roll 6 and so on to the printing plate. Roller 1 is formedas a hollow cylinder upon which are slide rings 8 whose surfaces areinclined with respect to the longitudinal axis of roller ll. These ringsmay be of different widths and are spaced from one another in such amanner that their surf-ace areas overlap longitudinally of the roller.Rings 8 are keyed against turning on roller 1 by means of spline '9. Aspindle it is mounted in a groove in the surface of roller 1 on aneccentric axis and, in turn, contains a dove-tail slot holding a stripof resilient material 11, such as rubber, which projects slightly out ofthe dovetail slot. Spindle it) has a square bolt head end 12 projectingthrough the flange plates 13 which are secured to the ends of roller 1by means of bolts .14. As spindle 10 is turned by bolt head 12, theresilient material 11 is brought into 'wedging engagement with the rings8 to secure them against longitudinal movement along the roller 1.

End rings 8a have their outer end side perpendicular to the axis ofroller 1. Rings of small width can be mounted close together adjacentthe end rings 8a in order to obtain a better transfer of moisture inthese end areas. When spindle 10 is loosened, the rings can bedistributed along the length of the roller 1 in accordance with themoisture requirements of the press and then secured against longitudinalmovement by the turning of spindle It In order to ensure a good transferof liquid, each ring 8 has a roughened surface and is coated with anettle-like cloth as shown at 81). Due to the inclined surfaces of therings, the surface of the swinging transfer roll 5 is appropriatelywetted during each revolution of roller 1 so that the requireddistribution of the moisture on the printing plate is assured.

Having now described the means by which the objects of the invention areobtained,

We claim:

1. A ductor roll for transferring moisture in an offset printing presscomprising a cylindrical roll, a plurality of rings concentricallymounted on said cylindrical roll and having their circumferentialsurfaces inclined with respect to the longitudinal axis of saidcylindrical roll, said rings being spaced from each other a distancesuch that the surface of one ring laps the surface of an adjacent ringduring one revolution of said cylindrical roll, and spindle meanseccentrically mounted on said cylindrical roll for adjustably securingsaid rings to said cylindrical roll.

2. A ductor roll as in claim 1, further comprising spline means forkeying said rings to said cylindrical roll.

3. A ductor roll as in claim 2, further comprising a strip of resilientmaterial joined to said spindle means and extending outwardly of thesurface of said spindle means for engagement with said rings.

4. A ductor roll as in claim 1, further comprising a longitudinal groovein the surface of said cylindrical roll, flanged plates secured to theends of said cylindrical roll,

4 said spindle being mounted in said groove and iournalled in saidflanged plates, and a square end on said spindle for turning saidspindle.

5. A ductor roll as in claim 1, said rings each having a roughened outercircumferential surface.

6. A ductor roll as in claim 1, said rings each being covered with anadhesive nettle cloth.

7. A ductor roll as in claim 1, further comprising end rings on saidcylindrical roll with each end ring having its outer side edge extendingperpendicular to the longitudinal axis of said cylindrical roll.

References Cited in the file of this patent UNITED STATES PATENTS958,440 Sackman May 17, 1910 FOREIGN PATENTS 601,883 Great Britain May13, 1948 731,530 Great Britain June 8, 1955

